Fluidic ejection device with optical blockage detector

ABSTRACT

The present disclosure is directed to a fluidic ejection device configured to detect whether one or more nozzles of the fluidic ejection device is in a normal state, a blocked nozzle state, or an accumulated fluid state. The fluidic ejection device includes an optical blockage detector having a light emitting device configured to emit a light signal, and a light sensor configured to detect the light signal. The optical blockage detector detects the normal state, the blocked nozzle state, and the accumulated fluid state based on the detected light signal.

BACKGROUND Technical Field

The present disclosure is directed to a fluidic device configured todetect blockage of one or more nozzles.

Description of the Related Art

Fluidic devices are used for a variety of applications. For example,fluidic devices are often used in printing applications, such as forimplementing printer heads for inkjet printers and 3D printers. Fluidicdevices are also often used in medical applications to eject, forexample, biological materials and drugs into patients.

Typically, fluidic devices include a plurality of nozzles in which fluidis ejected and dispensed from. Unfortunately, it is common for thesenozzles to become blocked or clogged with fluid when stored for longperiods of time or even during operation of the fluidic device.

The blockage of the nozzles prevents fluid from being ejected properlyfrom the nozzles. For printing applications, for example, blockage ofthe nozzles often results in text or images with portions being degradedor missing. In addition, blocked fluid, such as ink, may accumulate overtime and eventually protrude from a nozzle. Over time, the accumulatedfluid may hinder adjacent nozzles by blocking or deflecting fluidejected from the adjacent nozzles. This may eventually cause all of thenozzles of a fluidic device to malfunction.

BRIEF SUMMARY

The present disclosure is directed to a fluidic ejection deviceconfigured to detect whether or not one or more nozzles of the fluidicejection device is blocked or clogged. The fluidic ejection deviceincludes an optical blockage detector having a light emitting deviceconfigured to emit a light signal, and a light sensor configured todetect the light signal. The optical blockage detector determineswhether or not one or more nozzles of the fluidic ejection device isblocked based on the detected light signal.

Based on the detection results of the optical blockage detector, thefluidic ejection device may alter operation of the fluidic ejectiondevice. For example, the fluidic ejection device may halt operation ofthe fluidic ejection device. Alternatively, the fluidic ejection devicemay stop utilization of a blocked nozzle, and select an alternate nozzleto eject fluid from. As a result, fluid ejection errors may be avoided.For example, for printing applications, degradation of printed text orimages may be reduced. In addition, risk of accumulated fluid at ablocked nozzle, which may cause additional nozzles to malfunction, maybe avoided.

The optical blockage detector may be used to detect blocked nozzlesduring various phases of the fluidic ejection device. For example, theoptical blockage detector may be used during a manufacture phase toensure that the fluidic ejection device is functioning properly beforebeing deployed to a customer; during an operation phase (e.g., while thefluidic ejection device is ejecting fluid) to determine whetheroperation of the fluidic ejection device should be halted or adjusted;or during an idle phase (e.g., after the fluidic ejection device hasfinished ejecting fluid) to ensure that the fluidic ejection device isfunctioning properly for a subsequent ejection.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar featuresor elements. The size and relative positions of features in the drawingsare not necessarily drawn to scale.

FIG. 1 is a cross-sectional view of a fluid ejection device according toan embodiment disclosed herein.

FIG. 2 is a diagram showing signals of a fluid ejection device duringoperation according to an embodiment disclosed herein.

FIG. 3 shows readout circuitry according to an embodiment disclosedherein.

FIG. 4 is a diagram showing signals of the readout circuitry of FIG. 3during measurement of a light signal according to an embodimentdisclosed herein.

FIG. 5 shows a plurality of the readout circuitry of FIG. 3 according toan embodiment disclosed herein.

FIG. 6 shows a plurality of readout circuitry of FIG. 3 according toanother embodiment disclosed herein.

FIG. 7 shows readout circuitry according to another embodiment disclosedherein.

FIG. 8 is a diagram showing signals of the readout circuitry of FIG. 7during measurement of a light signal according to an embodimentdisclosed herein.

FIG. 9 shows a plurality of the readout circuitry of FIG. 7 according toan embodiment disclosed herein.

FIG. 10 shows a plurality of readout circuitry of FIG. 7 according toanother embodiment disclosed herein.

FIG. 11 shows readout circuitry according to another embodimentdisclosed herein.

FIG. 12 is a diagram showing signals of the readout circuitry of FIG. 11during measurement of a light signal according to an embodimentdisclosed herein.

FIG. 13 shows a plurality of the readout circuitry of FIG. 11 accordingto an embodiment disclosed herein.

FIG. 14 shows a plurality of readout circuitry of FIG. 11 according toanother embodiment disclosed herein.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various aspects of thedisclosed subject matter. However, the disclosed subject matter may bepracticed without these specific details. In some instances, well-knownstructures and methods of manufacturing fluidic devices, light emittingdevices, light sensors, integrated circuits, counters, and electricalcomponents (e.g., transistors, resistors, capacitors, etc.) have notbeen described in detail to avoid obscuring the descriptions of otheraspects of the present disclosure.

Unless the context requires otherwise, throughout the specification andclaims that follow, the word “comprise” and variations thereof, such as“comprises” and “comprising,” are to be construed in an open, inclusivesense, that is, as “including, but not limited to.”

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearance of the phrases “in oneembodiment” or “in an embodiment” in various places throughout thespecification are not necessarily all referring to the same aspect.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more aspects of the presentdisclosure.

Reference throughout the specification to integrated circuits isgenerally intended to include integrated circuit components built onsemiconducting or glass substrates, whether or not the components arecoupled together into a circuit or able to be interconnected. Throughoutthe specification, the term “layer” is used in its broadest sense toinclude a thin film, a cap, or the like, and one layer may be composedof multiple sub-layers.

It is noted that the dimensions set forth herein are provided asexamples. Other dimensions are envisioned for this embodiment and allother embodiments of this application.

FIG. 1 is a cross-sectional view of a fluidic ejection device 10according to an embodiment disclosed herein.

The fluidic ejection device 10 ejects fluid into a surroundingenvironment of the fluidic ejection device 10. The fluidic ejectiondevice 10 may be used for a plurality of different applications. Forexample, the fluidic ejection device 10 may be included in a printerhead for a printer, such as an inkjet printer and 3D printer, todispense ink. As another example, the fluidic ejection device 10 may beincluded in a medical device to inject fluid, such as biologicalmaterials and drugs, into a patient. The fluidic ejection device 10includes a substrate 12, an inlet 14, a fluid ejector 16, a firststructural layer 18, a chamber 20, a feed channel 22, a secondstructural layer 24, a nozzle 26, an optical blockage detector 28, and alight shield 54.

The substrate 12 provides a platform for the fluidic ejection device 10.The substrate 12 may be made of any rigid material. In one embodiment,the substrate 12 include semiconductor material, such as silicon.

The inlet 14 is a through hole that extends through the substrate 12.The inlet 14 provides an input channel to receive fluid 29, such as ink,from a reservoir of the fluid 29. The inlet 14 is fluidically coupled tothe reservoir and the chamber 20. The inlet 14 receives the fluid 29from the reservoir, and outputs the fluid 29 into the chamber 20. Thefluid 29 flows through the inlet 14 moves in a direction 30.

The fluid ejector 16 is in or on the substrate 12. The fluid ejector 16ejects the fluid 29 stored in the chamber 20, through the feed channel22, and out of the nozzle 26. Fluid flowing out of the chamber 20 movesin a direction 32. The fluid ejector 16 may be any ejection deviceconfigured to dispense fluid. In one embodiment, the fluid ejector 16includes an actuator, such as a piezoelectric actuator, that pushesfluid out of the nozzle 26. In one embodiment, the fluid ejector 16 usesthermal techniques that heats fluid in the chamber 20 with a heatingelement until fluid is dispensed from the nozzle 26.

The first structural layer 18 is on the substrate 12. The firststructural layer 18 provides structure for the chamber 20 and the feedchannel 22. In one embodiment, the first structural layer 18 includessemiconductor material, such as silicon.

The chamber 20 is formed in the first structural layer 18. The chamber20 is a cavity in the fluidic ejection device 10 that holds the fluid 29received from the reservoir of the fluid 29. The chamber 20 isfluidically coupled to the inlet 14 and the feed channel 22. Asdiscussed above, the fluid ejector 16 ejects the fluid 29 stored in thechamber 20, through the feed channel 22, and out of the nozzle 26 in thedirection 32.

The feed channel 22 is formed in the first structural layer 18, anddirectly overlies the chamber 20. The feed channel 22 provides an outputchannel for dispensing the fluid 29 from in the chamber 20 and out ofthe nozzle 26. The feed channel 22 is fluidically coupled to the chamber20 and the nozzle 26. The fluid 29 flowing through the feed channel 22moves in the direction 32.

The second structural layer 24 is on the first structural layer 18. Thesecond structural layer 24 provides structure for the nozzle 26. In oneembodiment, the second structural layer 24 include semiconductormaterial, such as silicon.

The nozzle 26 is a through hole or opening that extends through thesecond structural layer 24. The nozzle 26 provides an output channel fordispensing the fluid 29 from the chamber 20 into a surroundingenvironment of the fluidic ejection device 10. The nozzle 26 isfluidically coupled to the feed channel 22 and the surroundingenvironment of the fluidic ejection device 10. The fluid 29 flowing outof the nozzle 26 moves in the direction 32.

As discussed above, the inlet 14 is fluidically coupled to the reservoirof the fluid 29 and the chamber 20, the chamber 20 is fluidicallycoupled to the inlet 14 and the feed channel 22, the feed channel 22 isfluidically coupled to the chamber 20 and the nozzle 26, and the nozzle26 is fluidically coupled to the feed channel 22 and a surroundingenvironment. As a result, the reservoir, the inlet 14, the chamber 20,the feed channel 22, the nozzle 26, and the surrounding environment arefluidically coupled to each other.

The optical blockage detector 28 is in or on the second structural layer24. The optical blockage detector 28 detects whether or not the nozzle26 is blocked or clogged with the fluid 29. The optical blockagedetector 28 includes a light emitting device 34, a light sensor 36, andcontrol circuitry 38.

The light emitting device 34 emits a light signal 40 towards the nozzle26.

The light signal 40 travels from the light emitting device 34 towards aside 42 of the nozzle 26 that faces the surrounding environment of thefluidic ejection device 10. The light emitting device 34 may be any typeof device that transmits light. In one embodiment, as will be discussedin further detail below, the light emitting device 34 is a lightemitting diode (LED).

In one embodiment, the light emitting device 34 emits a light signalthat is transparent to the fluid 29. Stated differently, the lightemitting device 34 emits a light signal that is configured to transmitthrough the fluid 29 such that the light signal 40 is able to propagatethrough the fluid 29 and to the light sensor 36. In one embodiment, thelight emitting device 34 emits an infrared light signal. In oneembodiment, the light emitting device 34 emits a white light signal.Operation of the light emitting device 34 during detection of a blockednozzle will be discussed in further detail below.

The light emitting device 34 may have multiple positions. In oneembodiment, as shown in FIG. 1, the light emitting device 34 ispositioned on the second structural layer 24. In one embodiment, thesecond structural layer 24 is a semiconductor substrate, and the lightemitting device 34 is fabricated directly in the second structural layer24. In one embodiment, the light emitting device 34 is positioned off ofthe fluidic ejection device 10 (e.g., the light emitting device 34 maybe positioned off chip and elsewhere within a device housing the fluidicejection device 10).

The light sensor 36 detects the light signal 40 emitted from the lightemitting device 34. The light sensor 36 may be any type of device thatdetects light. In one embodiment, as will be discussed in further detailbelow, the light sensor 36 is a photodiode.

The strength of the light signal detected by the light sensor 36 isdependent on whether or not a droplet 44 of the fluid 29 is present inthe nozzle 26 and on the side 42 of the nozzle 26. If the droplet 44 ispresent as shown in FIG. 1, the light signal 40 will refract at asurface of the droplet 44, and a refracted light signal 46 of the lightsignal 40 will transmit towards the light sensor 36. In this case, thelight signal detected by the light sensor 36 (e.g., the refracted lightsignal 46) will be strong. Conversely, if the droplet 44 is not present,the light signal 40 will stay on its current path and continue as lightsignal 48. In this case, the light signal, if any, detected by the lightsensor 36 will be weak. Accordingly, the strength of the light signaldetected by the light sensor 36 indicates whether the droplet 44 of thefluid 29 is present, and can be used to determine whether or not thenozzle 26 is blocked or clogged. Operation of the light sensor 36 duringdetection of a blocked nozzle will be discussed in further detail below.

In one embodiment, the light sensor 36 is positioned on the firststructural layer 18 and adjacent to the nozzle 26. In one embodiment,the second structural layer 24 is a semiconductor substrate, and thelight sensor 36 is fabricated directly in the second structural layer24.

In one embodiment, as shown in FIG. 1, the light emitting device 34 andthe light sensor 36 are positioned on opposite sides of the nozzle 26.Stated differently, the light emitting device 34 is positioned on afirst side of the nozzle 26, and the light sensor 36 is positioned on asecond side, opposite to the first side, of the nozzle 26.

In one embodiment, the light sensor 36 is positioned flush with asidewall 50 of the nozzle 26. In this embodiment, the light sensor 36forms a portion of the sidewall 50 of the nozzle 26.

In one embodiment, a light receiving surface of the light sensor 36(e.g., a side of the light sensor 36 that detects light) faces thesidewall 50 of the nozzle 26 and the light emitter 34.

In one embodiment, as shown in FIG. 1, the light sensor 36 is spacedfrom a sidewall 50 of the nozzle 26 by a distance 52. The distance 52 isset such that a light signal, such as the refracted light signal 46, isable to penetrate through the second structural layer 24 and reach thelight sensor 36. For example, in one embodiment, the second structurallayer 24 include semiconductor material, such as silicon. In thisembodiment, light photons will penetrate and get absorbed thesemiconductor material. The absorbed light photons will then generate acharge that is detectable by the light sensor 36. In one embodiment, thedistance 52 is between 10 and 50 micrometers.

Covering the light sensor 36 with the second structural layer 24 andpositioning the light sensor 36 away from the sidewall 50 of the nozzle26 protects the light sensor 36 from being damaged. For example, duringfabrication of the fluidic ejection device 10, the second structurallayer 24 may protect the light sensor 35 from etchants used to form thenozzle 26. As another example, during operation of the fluidic ejectiondevice 10, the second structural layer 24 may protect the light sensor35 from the fluid 29 repeatedly moving through the nozzle 26.

The control circuitry 38 is electrically coupled to the fluid ejector16, the light emitting device 34, and the light sensor 36.

The control circuitry 38 controls the fluidic ejection device 10 toeject the fluid 29 during operation of the fluid ejection device 10.During operation of the fluidic ejection device 10, the controlcircuitry 38 provides a control signal to the fluid ejector 16 toinstruct the fluid ejector 16 to eject the fluid 29 stored in thechamber 20, through the feed channel, and out of the nozzle 26.

The control circuitry 38 also controls the fluidic ejection device 10 todetect a normal state, a blocked nozzle state, and an accumulated fluidstate of the fluidic ejection device 10. During detection, the controlcircuitry 38 provides control signals (e.g., a drive signals) to thelight emitting device 34 to instruct the light emitting device 34 toemit light signals (e.g., the light signal 40) towards the nozzle 26,and provides control signals to the light sensor 36 to instruct thelight sensor 36 to detect the light signals emitted from the lightemitting device 34. The control circuitry 38 then receives and readselectrical signals from the light sensor 36 via readout circuitry; anduses the electrical signals from the light sensor 36 to determinewhether or not the fluidic ejection device 10 is in the normal state,the blocked nozzle state, or the accumulated fluid state. The detectionof the normal state, the blocked nozzle state, and the accumulated fluidstate; and the readout circuitry included in the control circuitry 38will be discussed in further detail below.

The control circuitry 38 may have multiple positions. In one embodiment,as shown in FIG. 1, the control circuitry 38 is positioned on the firststructural layer 18 and adjacent to the light sensor 36. In oneembodiment, the second structural layer 24 is a semiconductor substrate,and the control circuitry 38 is fabricated directly in the secondstructural layer 24. In one embodiment, the control circuitry 38 ispositioned off of the fluidic ejection device 10 (e.g., off chip).

The light shield 54 is on the second structural layer 24, and directlyoverlies the light sensor 36 and the control circuitry 38. The lightshield 54 prevents light signals in the surrounding environment of thefluidic ejection device 10 from interfering with, for example, therefracted light signal 46. Thus, noise in a light signal measured by thelight sensor 36 is reduced, and accuracy of the light sensor 36 isimproved. In one embodiment, the light shield 54 is a conductive layer,such as a metal layer.

Although a single inlet 14, fluid ejector 16, chamber 20, feed channel22, nozzle 26, and optical blockage detector 28 are shown in FIG. 1, thefluidic ejection device 10 may have other configurations with any numberof inlets, fluid ejectors, feed channels, nozzles, and optical blockagedetectors.

In one embodiment, the structure shown in FIG. 1 is repeated such thatthe fluidic ejection device 10 includes multiple inlets, fluid ejectors,chambers, feed channels, nozzles, and optical blockage detectors. Inthis embodiment, the fluidic ejection device 10 is able eject fluid frommultiple nozzles at once, or switch between one or more nozzles of themultiple nozzles for ejecting fluid. Each of the optical blockagedetectors detects whether or not a respective nozzle is blocked orclogged with the fluid.

In one embodiment, an inlet, fluid ejector, and chamber are sharedbetween multiple feed channels, nozzles, and optical blockage detectors.In this embodiment, fluid ejected from the nozzles comes from the samechamber.

The fluidic ejection device 10 is configured to determine whether thefluidic ejection device 10 is in a normal state, a blocked nozzle state,or an accumulated fluid state. FIG. 2 is a diagram showing signals ofthe fluidic ejection device 10 during operation according to anembodiment disclosed herein. Namely, FIG. 2 shows an ejection signal 56,a fluid size signal 58, a light emitting device drive signal 60, and adetected light signal 62 for the normal state, the blocked nozzle state,and the accumulated fluid state of the fluidic ejection device 10.

The ejection signal 56, fluid size signal 58, light emitting devicedrive signal 60, and detected light signal 62 are shown along a timeaxis (horizontal axis in FIG. 2) and an amplitude axis (vertical axis inFIG. 2). The time axis may have any time unit, such as nanoseconds,microseconds, milliseconds, seconds, etc. The amplitude axis may haveany amplitude unit, such as volts, amps, etc.

The ejection signal 56 controls ejection of fluid from the fluidicejection device 10. For example, the control circuitry 38 generates andprovides the ejection signal 56 to the fluid ejector 16 to instruct thefluid ejector 16 to eject the fluid 29 out of the nozzle 26. In oneembodiment, the fluid ejector 16 ejects the fluid 29 out of the nozzle26 when the ejection signal 56 is in a high state (e.g., above apredetermined threshold), and does not eject the fluid 29 out of thenozzle 26 when the ejection signal 56 is in a low state (e.g., below apredetermined threshold). The ejection signal 56 may be any type ofelectrical signal, such as a voltage signal, current signal, etc.

The fluid size signal 58 indicates a size or an amount of fluid at or ina head of a nozzle detected by the fluidic ejection device 10. A largeor high fluid size signal (e.g., above a predetermined threshold)indicates that fluid is present at or in a head of a nozzle, and a smallor low fluid size signal (e.g., below a predetermined threshold)indicates that fluid is not present at or in a head of a nozzle. Forexample, a large or high fluid size signal 58 indicates that the droplet44 of the fluid 29 is present at the nozzle 26. Conversely, a low orsmall fluid size signal 58 indicates that the droplet 44 of the fluid 29is not present at the nozzle 26.

The light emitting device drive signal 60 controls the fluidic ejectiondevice 10 to emit a light signal during detection of the normal state,the blocked nozzle state, and the accumulated fluid state. For example,the control circuitry 38 generates and provides the light emittingdevice drive signal 60 to the light emitting device 34 such that thelight emitting device 34 to emits the light signal 40 towards the lightsensor 36. In one embodiment, the light emitting device 34 emits thelight signal 40 when the light emitting device drive signal 60 is in ahigh state (e.g., above a predetermined threshold), and does not emitthe light signal 40 when the light emitting device drive signal 60 is ina low state (e.g., below a predetermined threshold). The light emittingdevice drive signal 60 may be any type of electrical signal, such as avoltage signal, current signal, etc.

The detected light signal 62 is a detected light signal by the fluidicejection device 10 during detection of the normal state, the blockednozzle state, and the accumulated fluid state. For example, the detectedlight signal 62 is the refracted light signal 46 of the light signal 40detected by the light sensor 36. The detected light signal 62 indicateswhether or not fluid is present at or in a nozzle. As discussed above,if the droplet 44 is present as shown in FIG. 1, the light signal 40will refract at a surface of the droplet 44, and a refracted lightsignal 46 of the light signal 40 will transmit towards the light sensor36. In this case, the detected light signal 62 will be large or high(e.g., above a predetermined threshold). Stated differently, thedetected light signal will be large or high when the fluid detection thefluid size signal 58 is high. Conversely, if the droplet 44 is notpresent, the light signal 40 will stay on its current path and continueas light signal 48. In this case, the detected light signal 62 will besmall or low (e.g., below a predetermined threshold). Stateddifferently, the detected light signal will be small or low when thefluid detection the fluid size signal 58 is low. The detected lightsignal 62 may be any type of electrical signal, such as a voltagesignal, current signal, etc.

In the normal state, the fluidic ejection device 10 is functioningproperly. For example, the fluidic ejection device 10 ejects fluid viathe nozzle 26 when the fluid ejector 16 receives the ejection signal 56,and does not eject fluid via the nozzle 26 when the fluid ejector 16does not receive the ejection signal 56. In the normal state, fluid isdetected on the side 42 of the nozzle 26 when fluid is ejected via thenozzle 26 (i.e., when the fluid ejector 16 receives the ejection signal56); and fluid is not detected on the side 42 of the nozzle 26 whenfluid is not ejected via the nozzle 26 (i.e., when the fluid ejector 16does not receive the ejection signal 56), as fluid is not stuck on or inthe nozzle 26.

In the blocked nozzle state, the nozzle 26 is clogged with, for example,old fluid, and the fluid 29 is unable to eject out of the nozzle 26. Forexample, the fluidic ejection device 10 does not eject fluid out of thenozzle 26 when the fluid ejector 16 receives the ejection signal 56, anddoes not eject fluid via the nozzle 26 when the fluid ejector 16 doesnot receive the ejection signal 56. In the blocked nozzle state, fluidis not detected on the side 42 of the nozzle 26 when fluid is ejectedvia the nozzle 26 (i.e., when the fluid ejector 16 receives the ejectionsignal 56); and fluid is not detected on the side 42 of the nozzle 26when fluid is not ejected via the nozzle 26 (i.e., when the fluidejector 16 does not receive the ejection signal 56), as fluid is notstuck on or in the nozzle 26.

In the accumulated fluid state, fluid gathers in and/or on the nozzle26. For example, the fluidic ejection device 10 may or may not ejectfluid via the nozzle 26 when the fluid ejector 16 receives the ejectionsignal 56, and does not eject fluid via the nozzle 26 when the fluidejector 16 does not receive the ejection signal 56. In the accumulatedfluid state, fluid is still detected on the side 42 of the nozzle 26when fluid is not ejected via the nozzle 26 (i.e., when the fluidejector 16 does not receive the ejection signal 56). If the fluidicejection device 10 is in the accumulated fluid state for prolongedperiods of time, the accumulated fluid state may eventually lead to theblocked nozzle state.

The fluidic ejection device 10 determines whether a nozzle (e.g., thenozzle 26) is in the normal state, the blocked nozzle state, or theaccumulated fluid state based on the detected light signal 62 during anejection detection period 68, and the detected light signal 62 during anon-ejection detection period 70.

During the ejection detection period 68, the control circuitry 38instructs ejection of fluid from the nozzle 26 (i.e., instructs thefluid ejection device 10 to eject fluid from the nozzle 26) and detectsthe detected light signal 62. For example, the control circuitry 38provides the ejection signal 56 to the fluid ejector 16, provides thelight emitting device drive signal 60 to the light emitting device 34,and detects the detected light signal 62. If the fluidic ejection device10 is functioning properly, the detected light signal 62 indicates fluidis present at or in a head of a nozzle (e.g., the detected light signal62 has a value above a predetermined threshold) during the firstdetection period.

During the non-ejection detection period 70, the control circuitry 38does not instruct ejection of fluid from the nozzle 26 (i.e., instructsthe fluid ejection device 10 to not eject fluid from the nozzle 26) anddetects the detected light signal 62. For example, the control circuitry38 does not provide the ejection signal 56 to the fluid ejector 16, butprovides the light emitting device drive signal 60 to the light emittingdevice 34, and detects the detected light signal 62. If the fluidicejection device 10 is functioning properly, the detected light signal 62indicates fluid is not present at or in a head of a nozzle (i.e., thedetected light signal 62 has a value below a predetermined threshold)during the second detection period.

The fluidic ejection device 10, specifically the control circuitry 38,determines a nozzle (e.g., the nozzle 26) is in the normal state in acase where (1) the detected light signal 62 indicates fluid is presentat or in a head of a nozzle during the ejection detection period 68, and(2) the detected light signal 62 indicates fluid is not present at or ina head of the nozzle during the non-ejection period 70. For example, asshown in FIG. 2, the detected light signal 62 has a value above apredetermined threshold 72 during the ejection detection period 68, andhas a value below the predetermined threshold 72 during the non-ejectiondetection period 70.

The fluidic ejection device 10, specifically the control circuitry 38,determines a nozzle (e.g., the nozzle 26) is in the blocked nozzle statein a case where (1) the detected light signal 62 indicates fluid is notpresent at or in a head of a nozzle during the ejection detection period68, and (2) the detected light signal 62 indicates fluid is not presentat or in a head of the nozzle during the non-ejection period 70. Forexample, as shown in FIG. 2, the detected light signal 62 has a valuebelow the predetermined threshold 72 during the ejection detectionperiod 68 and the non-ejection detection period 70.

The fluidic ejection device 10, specifically the control circuitry 38,determines a nozzle (e.g., the nozzle 26) is in the blocked nozzle statein a case where (1) the detected light signal 62 indicates fluid ispresent at or in a head of a nozzle during the ejection detection period68, and (2) the detected light signal 62 indicates fluid is present ator in a head of the nozzle during the non-ejection period 70. Forexample, as shown in FIG. 2, the detected light signal 62 has a valueabove the predetermined threshold 72 during the ejection detectionperiod 68 and the non-ejection detection period 70.

The control circuitry 38 adjusts operation of the fluidic ejectiondevice 10 based on whether a nozzle (e.g., the nozzle 26) is in thenormal state, the blocked nozzle state, or the accumulated fluid state.

In one embodiment, the control circuitry 38 continues operation of anozzle determined to be in a normal state or in an accumulated fluidstate.

In one embodiment, the control circuitry stops operation of the fluidicejection device 10 (i.e., stops operation of all of the fluidicejections device's 10 nozzles) in response to determining apredetermined number of nozzles (e.g., 1, 10, 50, or 100 nozzles) are ina blocked nozzle state or in an accumulated fluid state.

In one embodiment, the control circuitry 38 halts operation of aspecific nozzle determined to be in a blocked nozzle state or in anaccumulated fluid state, but continues operation of other nozzles in anormal state. In one embodiment, the control circuitry 38 haltsoperation of a nozzle determined to be in a blocked nozzle state or inan accumulated fluid state, and activates a secondary nozzle (e.g., anozzle not currently in use) to replace the nozzle in the blocked nozzlestate or the accumulated fluid state.

By altering operation of the fluidic ejection device 10 based on whetherone or more nozzles is in the normal state, the blocked nozzle state, orthe accumulated fluid state, fluid ejection errors may be avoided. Forexample, for printing applications, degradation of printed text orimages may be reduced. In addition, risk of accumulated fluid at ablocked nozzle causing additional nozzles to malfunction may be avoided.

The fluidic ejection device 10 may determine whether nozzles are in thenormal state, the blocked nozzle state, or the accumulated fluid stateduring various operational phases of the fluidic ejection device. Forexample, the fluidic ejection device 10 may determine the state of oneor more nozzles during a manufacture phase to ensure that the fluidicejection device is functioning properly before being deployed to acustomer. The fluidic ejection device 10 may also determine the state ofone or more nozzles being used during an operational phase (e.g., whilethe fluidic ejection device is ejecting fluid) to determine whetheroperation of the fluidic ejection device should be halted or adjusted.Further, the fluidic ejection device 10 may determine the state of oneor more nozzles during an idle phase (e.g., after the fluidic ejectiondevice has finished ejecting fluid) to ensure that the fluidic ejectiondevice is functioning properly for a subsequent ejection.

As discussed above, the control circuitry 38 receives and readselectrical signals from the light sensor 36 via readout circuitry; anduses the electrical signals from the light sensor 36 to determinewhether or not the fluidic ejection device 10 is in the normal state,the blocked nozzle state, or the accumulated fluid state. FIG. 3 showsreadout circuitry 74 according to an embodiment disclosed herein.

In one embodiment, the readout circuitry 74 is a part of the controlcircuitry 38. In one embodiment, the readout circuitry 74 is separatefrom the control circuitry 38 and positioned on the fluidic ejectiondevice 10 (e.g., on the second structural layer 24 shown in FIG. 1). Inone embodiment, the readout circuitry 74 is separate from the controlcircuitry 38 and positioned off of the fluidic ejection device 10 (e.g.,off chip).

The readout circuitry 74 includes a first input 76, a second input 78, athird input 80, a first transistor 82, a second transistor 84, and anoutput 86. In the embodiment, as shown in FIG. 3, the light sensor 36 isa photodiode. Other types of light sensors are also possible. The firstinput 76 is electrically coupled to the drain of the first transistor 82and the drain of the second transistor 84. The first input 76 receives afirst input signal VRT. The first input signal VRT may be any type ofelectrical signal, such as a voltage signal, current signal, etc.

The second input 78 is electrically coupled to the gate of the firsttransistor 82. The second input 78 receives a reset signal RST. Thereset signal RST may be any type of electrical signal, such as a voltagesignal, current signal, etc.

The third input 80 is electrically coupled to the anode of the lightsensor 36. The third input 80 receives a second input signal VSS. Thesecond input signal VSS may be any type of electrical signal, such as avoltage signal, current signal, etc. In one embodiment, the second inputsignal VSS is set to ground.

The drain of the first transistor 82 is electrically coupled to thefirst input 76 and the drain of the second transistor 84, the gate ofthe first transistor 82 is electrically coupled to the second input 78,and the source of the first transistor 82 is electrically coupled to thecathode of the light sensor 36. A first output signal VPD is output fromthe source of the first transistor 82. The first output signal VPD maybe any type of electrical signal, such as a voltage signal, currentsignal, etc.

The drain of the second transistor 84 is electrically coupled to thedrain of the first transistor 82 and the first input 76, the gate of thesecond transistor 84 is electrically coupled to the source of the firsttransistor 82 and the cathode of the light sensor 36, and the source ofthe second transistor 84 is electrically coupled to the output 86. Thegate of the second transistor 84 receives the first output signal VPD. Asecond output signal VSF is output from the source of the secondtransistor 84. The second output signal VSF may be any type ofelectrical signal, such as a voltage signal, current signal, etc.

The output 86 is electrically coupled to the source of the secondtransistor 84. The output 86 receives the second output signal VSF, andoutputs the second output signal VSF to processing circuitry todetermine the detected light signal 62.

In one embodiment, the processing circuitry is a part of the controlcircuitry 38. In one embodiment, the processing circuitry is separatefrom the control circuitry 38 and positioned on the fluidic ejectiondevice 10 (e.g., on the second structural layer 24 shown in FIG. 1). Inone embodiment, the processing circuitry is separate from the controlcircuitry 38 and positioned off of the fluidic ejection device 10 (e.g.,off chip).

In one embodiment, the processing circuitry includes sample and holdcircuitry configured to sample a value of the second output signal VSF,and hold the sampled value of the second output signal VSF. Theprocessing circuitry then determines the detected light signal 62 basedon the sampled value. For example, in one embodiment, the processingcircuitry outputs a detected light signal 62 having a large or highvalue (e.g., above a predetermined threshold) in response to the sampledvalue being below a predetermined threshold. Conversely, in oneembodiment, the processing circuitry outputs a detected light signal 62having a large or high value (e.g., above a predetermined threshold) inresponse to the sampled value being above a predetermined threshold.

In one embodiment, the processing circuitry includes an analog-digitalconverter configured to convert the output signal VSF from an analogsignal to a digital signal. The processing circuitry then determines thedetected light signal 62 based on the digital signal. For example, inone embodiment, the processing circuitry outputs a detected light signal62 having a large or high value (e.g., above a predetermined threshold)in response to the digital signal having a low digital value (e.g.,below a predetermined threshold). Conversely, in one embodiment, theprocessing circuitry outputs a detected light signal 62 having a largeor high value (e.g., above a predetermined threshold) in response to thedigital signal having a high digital value (e.g., above a predeterminedthreshold).

In one embodiment, the first input signal VRT, the reset signal RST, andthe second input signal VSS is provided by the control circuitry 38,itself. For example, the control circuitry 38 generates and applies thefirst input signal VRT, the reset signal RST, and the second inputsignal VSS to the first input 76, the second input 78, and the thirdinput 80, respectively. In one embodiment, the first input signal VRT,the reset signal RST, and the second input signal VSS is generatedoutside of the fluidic ejection device 10 (e.g., off chip). For example,circuitry outside of the fluidic ejection device 10 generates andapplies the first input signal VRT, the reset signal RST, and the secondinput signal VSS to the first input 76, the second input 78, and thethird input 80, respectively.

FIG. 4 is a diagram showing signals of the readout circuitry 74 duringmeasurement of a light signal according to an embodiment disclosedherein. Namely, FIG. 4 shows the light emitting device drive signal 60,the reset signal RST, the first output signal VPD, and the second outputsignal VSF during measurement of a light signal (e.g., during theejection detection period 68 and the non-ejection detection period 70).

The light emitting device drive signal 60, the reset signal RST, thefirst output signal VPD, and the second output signal VSF are shownalong a time axis (horizontal axis in FIG. 4) and an amplitude axis(vertical axis in FIG. 4). The time axis may have any time unit, such asnanoseconds, microseconds, milliseconds, seconds, etc. The amplitudeaxis may have any amplitude unit, such as volts, amps, etc.

In the embodiment shown in FIG. 4, the second input signal VSS is set toground.

Between time t1 and time t2, the fluidic ejection device 10 is preparedfor measuring a light signal. The light emitting device drive signal 60is set to a low state such that the light emitting device 34 does notemit the light signal 40. In one embodiment, the light emitting devicedrive signal 60 is between 0 and 3 volts. In addition, the reset signalRST is set to a high state to clear the readout circuitry 74 of anyresidual electrical signals from a previous measurement. In oneembodiment, the reset signal RST is between 3 and 6 volts. The firstoutput signal VPD has a constant value equal to the first input signalVRT. In one embodiment, the first input signal VRT is between 3 and 6volts. The second output signal VSF follows the first output signal VPDbut has a lower value than first output signal VPD. Thus, the secondoutput signal VSF also has a constant value but is lower than the firstoutput signal VPD. In one embodiment, the second output signal VSF isbetween 0.5 and 1 volt lower than the first output signal VPD.

Between time t2 and time t3, the amplitude values of the light emittingdevice drive signal 60, the first output signal VPD, and the secondoutput signal VSF remain the same as between time t1 and time t2.However, at time t2, the reset signal RST is set to a low state. In oneembodiment, the reset signal RST is between 0 and 3 volts.

Between time t3 and time t4, the fluidic ejection device 10 emits alight signal and measures the emitted light signal. The light emittingdevice drive signal 60 is set to a high state such that the lightemitting device 34 emits the light signal 40. In one embodiment, thelight emitting device drive signal 60 is between 3 and 6 volts. Thereset signal RST remains the same as between time t2 and time t3.

Between time t3 and time t4, the amplitude value of the first outputsignal VPD changes depending on an amount of light detected by the lightsensor 36. As discussed above, if the droplet 44 is not present, thelight signal 40 will stay on its current path and continue as lightsignal 48. In this case, the light sensor 36, which in the embodimentshown in FIG. 3 is a photodiode, will not generate an electricalcurrent, and the first output signal VPD will remain the same.Conversely, if the droplet 44 is present as shown in FIG. 1, the lightsignal 40 will refract at a surface of the droplet 44, and a refractedlight signal 46 of the light signal 40 will transmit towards the lightsensor 36. In this case, the light sensor 36 will generate an electricalcurrent, and the first output signal VPD will gradually decrease.

The rate of decrease of the first output signal VPD is proportional tothe strength of light detected by the light sensor 36. For example, FIG.4 shows the first output signal VPD for six different light levels. Asshown in FIG. 4, the rate of decrease of the first output signal VPDincreases as the strength of light detected by the light sensor 36increases.

As discussed above, the second output signal VSF follows the firstoutput signal VPD but has a lower value than first output signal VPD.Thus, between time t3 and time t4, the second output signal VSF has thesame shape as the first output signal VPD (e.g., gradually decreaseswith the first output signal VPD). In one embodiment, the second outputsignal VSF is between 0.5 and 1 volt lower than the first output signalVPD.

At time t4, the fluidic ejection device 10 stops emitting a lightsignal. The light emitting device drive signal 60 is set to a low statesuch that the light emitting device 34 does not emit the light signal40. In one embodiment, the light emitting device drive signal 60 isbetween 0 and 3 volts. The reset signal RST remains the same as betweentime t2 and time t3. The first output signal VPD and the second outputsignal VSF hold their values at time t4.

The amplitude value of the second output signal VSF at time t4 isindicative of the amount of light detected by the light sensor 36, and,thus, is indicative of whether fluid is present at or in the head of thenozzle 26. For example, referring to FIG. 1, if the droplet 44 is notpresent, the light signal 40 will stay on its current path and continueas light signal 48. In this case, the strength of light detected by thelight sensor 36 will be weak, and the second output signal VSF will belarge or high (e.g., above a predetermined threshold). Conversely, ifthe droplet 44 is present as shown in FIG. 1, the light signal 40 willrefract at a surface of the droplet 44, and a refracted light signal 46of the light signal 40 will transmit towards the light sensor 36. Inthis case, the strength of light detected by the light sensor 36 will bestrong, and the second output signal VSF will be small or low (e.g.,below a predetermined threshold).

As discussed above, in one embodiment, the structure shown in FIG. 1 isrepeated such that the fluidic ejection device 10 includes multipleinlets, fluid ejectors, chambers, feed channels, nozzles, and opticalblockage detectors. Each of the optical blockage detectors detectswhether or not a respective nozzle is blocked or clogged with the fluid.In this embodiment, the readout circuitry 74 shown in FIG. 3 is repeatedfor each of the optical blockage detectors. Stated differently, thefluidic ejection device 10 includes a plurality of the readout circuitrythat are in one-to-one correspondence with the plurality of opticalblockage detectors, and, thus, are in one-to-one correspondence with theplurality of nozzles. In one embodiment, the plurality of readoutcircuitry are arranged in parallel to each other.

FIG. 5 shows a plurality of the readout circuitry 74 according to anembodiment disclosed herein. In the embodiment shown in FIG. 5, tworeadout circuits 74 are shown. Each of the two readout circuits 74receives and reads electrical signals from a respective optical blockagedetector, more specifically a respective light sensor. Each of thereadout circuits 74 have the same configuration and components as thereadout circuitry 74 shown in FIG. 3.

The readout circuits 74 are arranged in parallel. Namely, each of thetwo readout circuits 74 output the second output signal VSF from theoutput 86. The second output signals VSF are output separately and inparallel with each other. Although two readout circuits 74 are shown inFIG. 5, the fluidic ejection device 10 may include any number of readoutcircuits. In one embodiment, the fluidic ejection device 10 includes areadout circuit for each nozzle (i.e., the number of readout circuits inthe fluidic ejection device 10 is equal to the number of nozzles in thefluidic ejection device 10).

FIG. 6 shows a plurality of the readout circuitry 74 according toanother embodiment disclosed herein. The embodiment shown in FIG. 6 issimilar to the embodiment shown in FIG. 5. For example, each of the tworeadout circuits 74 output the second output signal VSF separately andin parallel with each other. However, in contrast to the embodimentshown in FIG. 5, the second output signals VSF of the two readoutcircuitry 74 are multiplexed and electrically coupled to a single output90.

As shown in FIG. 6, the source of each of the second transistors 84 iselectrically coupled to a switch 88. The switches 88 are opened andclosed to electrically couple and decouple the readout circuitry 74 andthe output 90. When the switch 88 is closed, the second output signalVSF is transmitted to the output 90 via the switch 88 and is output assignal VOUT. For example, referring to FIG. 6, the switch 88 for theupper readout circuitry 74 is in a closed state. Thus, the second outputsignal VSF for the upper readout circuitry 74 will be outputted out ofthe output 90 as the signal VOUT. When the switch 88 is opened, thesecond output signal VS is not transmitted to the output 90. Forexample, referring to FIG. 6, the switch 88 for the lower readoutcircuitry 74 is in an opened state. Thus, the second output signal VSFfor the lower readout circuitry 74 will not be outputted out of theoutput 90. Accordingly, the second output signals VSF of the pluralityof readout circuitry 74 may be multiplexed by switching the switches 88between open and closed states. The switches 88 may be any type ofswitching component. For example, in one embodiment, the switches 88 areimplemented using transistors.

FIG. 7 shows readout circuitry 92 according to another embodimentdisclosed herein. Similar to the readout circuitry 74 shown in FIG. 3,the readout circuitry 92 includes the first input 76, the second input78, the third input 80, the first transistor 82, and the output 86.However, in contrast to the readout circuitry 74, the readout circuitry92 includes an operational amplifier 94 instead of the second transistor84. The operational amplifier 94 is electrically coupled to the firsttransistor 82 and the output 86.

The non-inverting input (+) of the operational amplifier 94 iselectrically coupled to the source of the first transistor 82. Thenon-inverting input receives the first output signal VPD from the sourceof the first transistor 82.

The inverting input (−) of the operational amplifier 94 receives areference signal VREF. The reference signal VREF may be any type ofelectrical signal, such as a voltage signal, current signal, etc. Thereference signal VREF is used to set a threshold value for switching thethird output signal VPWM from a low state to a high state.

In one embodiment, the reference signal VREF is provided by the controlcircuitry 38, itself. For example, the control circuitry 38 generatesand applies the reference signal VREF to the inverting input of theoperational amplifier 94. In one embodiment, the reference signal VREFis generated outside of the fluidic ejection device 10 (e.g., off chip).For example, circuitry outside of the fluidic ejection device 10generates and applies the reference signal VREF to the inverting inputof the operational amplifier 94.

The output of the operational amplifier 94 is electrically coupled tothe output 86. A third output signal VPWM is output from the operationalamplifier 94 to the output 86. The third output signal VPWM may be anytype of electrical signal, such as a voltage signal, current signal,etc.

The amplitude of the third output signal VPWM depends on the firstoutput signal VPD and the reference signal VREF. The third output signalVPWM is set to a low state when the first output signal VPD is greaterthan the reference signal VREF, and is set to a high state when thefirst output signal VPD is equal to or less than the reference signalVREF. In one embodiment, the third output signal VPWM is between 0 and 3volts in the low state. In one embodiment, third output signal VPWM isbetween 3 and 6 volts in the high state. In one embodiment, thereference signal VREF is between 2 and 4 volts.

FIG. 8 is a diagram showing signals of the readout circuitry 92 duringmeasurement of a light signal according to an embodiment disclosedherein. Namely, FIG. 8 shows the light emitting device drive signal 60,the reset signal RST, the first output signal VPD, and the third outputsignal VPWM during measurement of a light signal (e.g., during theejection detection period 68 and the non-ejection detection period 70).

The light emitting device drive signal 60, the reset signal RST, thefirst output signal VPD, and the third output signal VPWM are shownalong a time axis (horizontal axis in FIG. 8) and an amplitude axis(vertical axis in FIG. 8). The time axis may have any time unit, such asnanoseconds, microseconds, milliseconds, seconds, etc. The amplitudeaxis may have any amplitude unit, such as volts, amps, etc.

In the embodiment shown in FIG. 8, the second input signal VSS is set toground. In addition, the amplitude of the reference signal VREF is lessthan the amplitude of the first reference signal VRT. In one embodiment,as shown in FIG. 8, the reference signal VREF is kept at a constantvalue during the measurement of the light signal.

Between time t1 and time t2, as discussed above, the fluidic ejectiondevice 10 is prepared for measuring a light signal. Between time t1 andtime t2, the light emitting device drive signal 60 is set to a low statesuch that the light emitting device 34 does not emit the light signal40, the reset signal RST is set to a high state to clear the readoutcircuitry 74 of any residual electrical signals from a previousmeasurement, and the first output signal VPD has a constant value equalto the first input signal VRT. The third output signal VPWM is in thelow state because the first output signal VPD is greater than thereference signal VREF between time t1 and time t2.

Between time t2 and time t3, the amplitude values of the light emittingdevice drive signal 60, the first output signal VPD, and the thirdoutput signal VPWM remain the same as between time t1 and time t2.However, at time t2, the reset signal RST is set to a low state. In oneembodiment, the reset signal RST is between 0 and 3 volts.

Between time t3 and time t4, as discussed above, the fluidic ejectiondevice 10 emits a light signal and measures the emitted light signal.The light emitting device drive signal 60 is set to a high state suchthat the light emitting device 34 emits the light signal 40. The resetsignal RST remains the same as between time t2 and time t3.

The amplitude value of the first output signal VPD between time t3 andtime t4 changes depending on an amount of light detected by the lightsensor 36. As discussed above, if the droplet 44 is not present, thelight signal 40 will stay on its current path and continue as lightsignal 48. In this case, the light sensor 36, which in the embodimentshown in FIG. 7 is a photodiode, will not generate an electricalcurrent, and the first output signal VPD will remain the same.Conversely, if the droplet 44 is present as shown in FIG. 1, the lightsignal 40 will refract at a surface of the droplet 44, and a refractedlight signal 46 of the light signal 40 will transmit towards the lightsensor 36. In this case, the light sensor 36 will generate an electricalcurrent, and the first output signal VPD will gradually decrease.

The rate of decrease of the first output signal VPD is proportional tothe strength of light detected by the light sensor 36. For example, FIG.8 shows the first output signal VPD for six different light levels. Asshown in FIG. 8, the rate of decrease of the first output signal VPDincreases as the strength of light detected by the light sensor 36increases.

As discussed above, the third output signal VPWM switches from the lowstate to a high state when the first output signal VPD is equal to orless than the reference signal VREF. For example, FIG. 8 shows fourthird output signals VPWM corresponding to four first output signals VPDthat drop below the reference signal VREF.

At time t4, as discussed above, the fluidic ejection device 10 stopsemitting a light signal. The light emitting device drive signal 60 isset to a low state such that the light emitting device 34 does not emitthe light signal 40. The reset signal RST remains the same as betweentime t2 and time t3. The first output signal VPD and the third outputsignal VPWM hold their values at time t4.

The amplitude value of the third output signal VPWM at time t4 isindicative of the amount of light detected by the light sensor 36, and,thus, is indicative of whether fluid is present at or in the head of thenozzle 26. For example, referring to FIG. 1, if the droplet 44 is notpresent, the light signal 40 will stay on its current path and continueas light signal 48. In this case, the strength of light detected by thelight sensor 36 will be weak, and the third output signal VPWM will belarge or high (e.g., above the reference signal VREF). Conversely, ifthe droplet 44 is present as shown in FIG. 1, the light signal 40 willrefract at a surface of the droplet 44, and a refracted light signal 46of the light signal 40 will transmit towards the light sensor 36. Inthis case, the strength of light detected by the light sensor 36 will bestrong, and the third output signal VPWM will be small or low (e.g.,below the reference signal VREF).

As discussed with respect to FIGS. 5 and 6, readout circuitry may berepeated for each of a plurality of optical blockage detectors.

FIG. 9 shows a plurality of the readout circuitry 92 according to anembodiment disclosed herein. Similar to the embodiment shown in FIG. 5,two readout circuits 92 are shown. Each of the two readout circuits 92receives and reads electrical signals from a respective optical blockagedetector, more specifically a respective light sensor. Each of thereadout circuits 92 have the same configuration and components as thereadout circuitry 92 shown in FIG. 7.

The readout circuits 92 are arranged in parallel. Namely, each of thetwo readout circuits 92 output the third output signal VPWM from theoutput 86. The third output signal VPWM are output separately and inparallel with each other.

Although two readout circuits 92 are shown in FIG. 9, the fluidicejection device 10 may include any number of readout circuits. In oneembodiment, the fluidic ejection device 10 includes a readout circuitfor each nozzle (i.e., the number of readout circuits in the fluidicejection device 10 is equal to the number of nozzles in the fluidicejection device 10).

FIG. 10 shows a plurality of readout circuitry 92 according to anotherembodiment disclosed herein. The embodiment shown in FIG. 10 is similarto the embodiment shown in FIG. 9. For example, each of the two readoutcircuits 92 output the third output signal VPWM separately and inparallel with each other. However, in contrast to the embodiment shownin FIG. 9, the third output signals VPWM of the two readout circuitry 92are multiplexed and electrically coupled to a single output 90.

As shown in FIG. 10, the output of each of the operational amplifiers 94is electrically coupled to a switch 88. The switches 88 are opened andclosed to electrically couple and decouple the readout circuitry 92 andthe output 90. When the switch 88 is closed, the third output signalVPWM is transmitted to the output 90 via the switch 88 and is output assignal VOUT. For example, referring to FIG. 10, the switch 88 for theupper readout circuitry 74 is in a closed state. Thus, the second outputsignal VSF for the upper readout circuitry 92 will be outputted out ofthe output 90 as the signal VOUT. When the switch 88 is opened, thethird output signal VPWM is not transmitted to the output 90. Forexample, referring to FIG. 6, the switch 88 for the lower readoutcircuitry 92 is in an open state. Thus, the third output signal VPWM forthe lower readout circuitry 92 will not be outputted out of the output90. Accordingly, the third output signals VPWM of the plurality ofreadout circuitry 92 may be multiplexed by switching the switches 88between open and closed states. The switches 88 may be any type ofswitching component. For example, in one embodiment, the switches 88 areimplemented using transistors.

FIG. 11 shows readout circuitry 96 according to another embodimentdisclosed herein. Similar to the readout circuitry 92 shown in FIG. 7,the readout circuitry 96 includes the first input 76, the second input78, the third input 80, the first transistor 82, the output 86, and theoperational amplifier 94. However, in contrast to the readout circuitry92, the inputs of the operational amplifier 94 are switched with eachother. Namely, the inverting input (−) is electrically coupled to thesource of the first transistor 82, and receives the first output signalVPD from the source of the first transistor 82; and the non-invertinginput (+) receives the reference signal VREF. In addition, the readoutcircuitry 96 includes a counter 98 positioned between the operationalamplifier 94 and the output 86.

As the inverting input (−) receives the first output signal VPD and thenon-inverting input receives the reference signal VREF, in theembodiment shown in FIG. 11, the third output signal VPWM is set to alow state when the first output signal VPD is less than the referencesignal VREF, and is set to a high state when the first output signal VPDis equal to or greater than the reference signal VREF.

The counter 98 is electrically coupled to the operational amplifier 94.The counter 98 receives the third output signal VPWM from theoperational amplifier 94, and receives a clock signal CLK received atinput 100.

The clock signal CLK is used by the counter 98 to increment a count. Inone embodiment, the counter 98 increments a count every rising edge ofthe clock signal CLK. In one embodiment, the counter 98 increments acount every falling edge of the clock signal CLK.

In one embodiment, the clock signal CLK is provided by the controlcircuitry 38, itself. For example, the control circuitry 38 generatesand applies the clock signal CLK to the counter 98. In one embodiment,the clock signal CLK is generated outside of the fluidic ejection device10 (e.g., off chip). For example, circuitry outside of the fluidicejection device 10 generates and applies the clock signal CLK to thecounter 98.

The counter 98 outputs a count value ADCOUT to the output 86. In oneembodiment, the count value ADCOUT is a digital value. The count valueADCOUT is proportional to the amount of light detected by the lightsensor 36, and, thus, is proportional to an amount of fluid present ator in the head of the nozzle 26. For example, a larger count value(e.g., hexadecimal value C) represents a large amount of light detectedby the light sensor 36, and, thus, a large amount of fluid present at orin the head of the nozzle 26. Conversely, a small count (e.g.,hexadecimal value 2) represents a small amount of light detected by thelight sensor 36, and, thus, a small amount of fluid present at or in thehead of the nozzle 26. As will be discussed in further detail below, thecount value ADCOUT is generated based on the third output signal VPWM.

FIG. 12 is a diagram showing signals of the readout circuitry 96 duringmeasurement of a light signal according to an embodiment disclosedherein. Namely, FIG. 12 shows the light emitting device drive signal 60,the reset signal RST, the first output signal VPD, the third outputsignal VPWM, and the count value ADCOUT during measurement of a lightsignal (e.g., during the ejection detection period 68 and thenon-ejection detection period 70).

The light emitting device drive signal 60, the reset signal RST, thefirst output signal VPD, and the third output signal VPWM are shownalong a time axis (horizontal axis in FIG. 12) and an amplitude axis(vertical axis in FIG. 12). The time axis may have any time unit, suchas nanoseconds, microseconds, milliseconds, seconds, etc. The amplitudeaxis may have any amplitude unit, such as volts, amps, etc. The countvalue ADCOUT is a digital value and is shown along the time axis.

In the embodiment shown in FIG. 12, the second input signal VSS is setto ground.

In contrast to the embodiment shown in FIG. 8, the reference signal VREFis not kept at a constant value during the measurement of the lightsignal. As shown in FIG. 12, between time t1 and time t4, the amplitudeof the reference signal VREF kept at a constant level that is greaterthan the amplitude of the first reference signal VRT. Subsequently, attime t4, the reference signal VREF ramps downward to zero. In oneembodiment, as shown in FIG. 12, the amplitude of the reference signalVREF decreases linearly to zero. As will be discussed in further detailbelow, the reference signal VREF is used in conjunction with the counter98 to provide a count value ADCOUT that is proportional to the amount oflight detected by the light sensor 36.

Between time t1 and time t2, as discussed above, the fluidic ejectiondevice 10 is prepared for measuring a light signal. Between time t1 andtime t2, the light emitting device drive signal 60 is set to a low statesuch that the light emitting device 34 does not emit the light signal40, the reset signal RST is set to a high state to clear the readoutcircuitry 74 of any residual electrical signals from a previousmeasurement, and the first output signal VPD has a constant value equalto the first input signal VRT. The third output signal VPWM is in thelow state because the first output signal VPD is less than the referencesignal VREF between time t1 and time t2.

Between time t2 and time t3, the amplitude values of the light emittingdevice drive signal 60, the first output signal VPD, and the thirdoutput signal VPWM remain the same as between time t1 and time t2.However, at time t2, the reset signal RST is set to a low state. In oneembodiment, the reset signal RST is between 0 and 3 volts.

Between time t3 and time t4, as discussed above, the fluidic ejectiondevice 10 emits a light signal and measures the emitted light signal.The light emitting device drive signal 60 is set to a high state suchthat the light emitting device 34 emits the light signal 40. The resetsignal RST and the third output signal VPWM remain the same as betweentime t2 and time t3.

The amplitude value of the first output signal VPD between time t3 andtime t4 changes depending on an amount of light detected by the lightsensor 36. As discussed above, if the droplet 44 is not present, thelight signal 40 will stay on its current path and continue as lightsignal 48. In this case, the light sensor 36, which in the embodimentshown in FIG. 7 is a photodiode, will not generate an electricalcurrent, and the first output signal VPD will remain the same.Conversely, if the droplet 44 is present as shown in FIG. 1, the lightsignal 40 will refract at a surface of the droplet 44, and a refractedlight signal 46 of the light signal 40 will transmit towards the lightsensor 36. In this case, the light sensor 36 will generate an electricalcurrent, and the first output signal VPD will gradually decrease.

As discussed above, the rate of decrease of the first output signal VPDis proportional to the strength of light detected by the light sensor36. For example, FIG. 12 shows the first output signal VPD for sixdifferent light levels. As shown in FIG. 12, the rate of decrease of thefirst output signal VPD increases as the strength of light detected bythe light sensor 36 increases.

At time t4, as discussed above, the fluidic ejection device 10 stopsemitting a light signal. The light emitting device drive signal 60 isset to a low state such that the light emitting device 34 does not emitthe light signal 40. The reset signal RST remains the same as betweentime t2 and time t3. The first output signal VPD hold its value at timet4.

In contrast to the embodiment shown in FIG. 8, the amplitude of thereference signal VREF begins decreasing at time t4. In one embodiment,as shown in FIG. 12, the amplitude of the reference signal VREF isdecreased linearly to zero. As discussed above, the third output signalVPWM switches from the low state to a high state when the first outputsignal VPD is equal to or greater than the reference signal VREF. As thereference signal VREF begins decreasing at time t4, the timing of thethird output signal VPWM switching to the high state depends on theamplitude of the first output signal VPD held at time t4. For example,FIG. 12 shows the first output signal VPD for six different lightlevels, and the corresponding third output signals VPWM for the sixdifferent light levels. As shown in FIG. 12, the third output signalVPWM will switch to a high state earlier (i.e., closer to time t4) whenthe first output signal VPD has a large amplitude (i.e., a weak lightsignal is detected). For example, the third output signal VPWM thatcorresponds to a weak detected light signal 102 switches to a high stateat time t5, and a third output signal VPWM that corresponds to a strongdetected light signal 104 switches to a high state at time t6.

The counter 98 starts a counter at time t4, and stops the counter whenthe third output signal VPWM switched to a high state. Subsequently, thecounter 98 outputs the value of the counter as the count value ADCOUT tothe output 86. In one embodiment, the counter 98 initiates a counter attime t4 and increments the counter every rising edge of the clock signalCLK. In one embodiment, the counter 98 initiates a counter at time t4and increments the counter every falling edge of the clock signal CLK.In one embodiment, the count value ADCOUT is a digital value.

The count value ADCOUT is proportional to the amount of light detectedby the light sensor 36, and, thus, is proportional to an amount of fluidpresent at or in the head of the nozzle 26. A small count value ADCOUTrepresents a small amount of light detected by the light sensor 36, and,thus, a small amount of fluid present at or in the head of the nozzle26. For example, referring to FIG. 12, the count value ADCOUT has ahexadecimal value 2 at time t5, which corresponds to the weak detectedlight signal 102. Conversely, a large count value ADCOUT represents alarge amount of light detected by the light sensor 36, and, thus, alarge amount of fluid present at or in the head of the nozzle 26. Forexample, referring to FIG. 12, the count value ADCOUT has a hexadecimalvalue C at time t6, which corresponds to the strong detected lightsignal 104.

As discussed with respect to FIGS. 5 and 6, readout circuitry may berepeated for each of a plurality of optical blockage detectors.

FIG. 13 shows a plurality of the readout circuitry 96 according to anembodiment disclosed herein. Similar to the embodiment shown in FIG. 5,two readout circuits 96 are shown. Each of the two readout circuits 96receives and reads electrical signals from a respective optical blockagedetector, more specifically a respective light sensor. Each of thereadout circuits 96 have the same configuration and components as thereadout circuitry 96 shown in FIG. 11.

The readout circuits 96 are arranged in parallel. Namely, each of thetwo readout circuits 96 output the count value ADCOUT from the output86. The count value ADCOUT are output separately and in parallel witheach other.

Although two readout circuits 96 are shown in FIG. 13, the fluidicejection device 10 may include any number of readout circuits. In oneembodiment, the fluidic ejection device 10 includes a readout circuitfor each nozzle (i.e., the number of readout circuits in the fluidicejection device 10 is equal to the number of nozzles in the fluidicejection device 10).

FIG. 14 shows a plurality of readout circuitry 96 according to anotherembodiment disclosed herein. The embodiment shown in FIG. 14 is similarto the embodiment shown in FIG. 13. For example, each of the two readoutcircuits 96 output the count value ADCOUT separately and in parallelwith each other. However, in contrast to the embodiment shown in FIG.13, the count value ADCOUT of the two readout circuitry 96 aremultiplexed and electrically coupled to a single output 106.

In the embodiment shown in FIG. 14, each of the counters 98 includes anoutput-enable OE input configured to receive a read signal. Each of thecounters 98 outputs the count value ADCOUT in response to receiving aread signal at the output-enable input OE. Namely, the counter 98 doesnot output the count value ADCOUT in response to receiving a disableread signal READ[0], and outputs the count value ADCOUT in response toreceiving an enable read signal READ[1]. For example, referring to FIG.14, the counter 98 for the upper readout circuitry 96 receives a disableread signal READ[0]. Thus, the count value ADCOUT for the upper readoutcircuitry 96 is not outputted out of the output 106. Conversely, thecounter 98 for the lower readout circuitry 96 receives an enable readsignal READ[1]. Thus, the count value ADCOUT for the lower readoutcircuitry 96 will be outputted out of the output 106. Accordingly, thecount value ADCOUT of the plurality of readout circuitry 96 may bemultiplexed by selectively supplying the disable read signal READ[0] andthe enable read signal READ[1] to the counters 98.

The various embodiments disclosed herein provide a fluidic ejectiondevice configured to detect whether one or more nozzles of the fluidicejection device is in a normal state, a blocked nozzle state, or anaccumulated fluid state. The fluidic ejection device includes an opticalblockage detector having a light emitting device configured to emit alight signal, and a light sensor configured to detect the light signal.The optical blockage detector detects the normal state, the blockednozzle state, and the accumulated fluid state based on the detectedlight signal.

According to one embodiment, a device includes a substrate, a firststructural layer on the substrate, a chamber between the substrate andthe first structural layer, a second structural layer on the firststructural layer, and a nozzle coupled to the chamber. The nozzle hassidewalls and extends through the second structural layer. The devicefurther includes a light emitter on the second structural layer, and alight receiver in the second structural layer and adjacent to thesidewalls of the nozzle.

According to one embodiment, a device includes a substrate, a firststructural layer on the substrate, a chamber between the substrate andthe first structural layer, a second structural layer on the firststructural layer, a nozzle having sidewalls and extending through thesecond structural layer, a light emitter on the second structural layer,a photodiode in the second structural layer and adjacent to thesidewalls of the nozzle, and readout circuitry including a firsttransistor and a second transistor. A source of the first transistor iselectrically coupled to a cathode of the photodiode, and a gate of thesecond transistor is electrically coupled to the source of the firsttransistor and the cathode of the photodiode.

According to one embodiment, a device includes a substrate, a firststructural layer on the substrate, a chamber between the substrate andthe first structural layer, a second structural layer on the firststructural layer, a nozzle having sidewalls and extending through thesecond structural layer, a light emitter on the second structural layer,a photodiode in the second structural layer and adjacent to thesidewalls of the nozzle, and readout circuitry including a transistorand an operational amplifier. A source of the transistor is electricallycoupled to a cathode of the photodiode, and the operational amplifierbeing is coupled to the source of the transistor and the cathode of thephotodiode.

According to one embodiment, a device includes a substrate, a firststructural layer on the substrate, a chamber between the substrate andthe first structural layer, a second structural layer on the firststructural layer, a nozzle having sidewalls and extending through thesecond structural layer, a light emitter on the second structural layer,a photodiode in the second structural layer and adjacent to thesidewalls of the nozzle, and readout circuitry including a transistor,an operational amplifier, and a counter. A source of the transistor iselectrically coupled to a cathode of the photodiode, the operationalamplifier is electrically coupled to the source of the transistor andthe cathode of the photodiode, and the counter is electrically coupledto the operational amplifier.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

1. A device, comprising: a substrate; a fluid ejector on the substrate;a chamber configured to hold a fluid; a feed channel fluidically coupledto the chamber; a nozzle fluidically coupled to the feed channel, thefluid ejector configured to eject the fluid from the chamber, throughthe feed channel, and out of the nozzle; a light emitting device on afirst side of the nozzle, the light emitting device configured totransmit a light signal; and a light sensor positioned on a second side,opposite to the first side, of the nozzle, the light sensor configuredto detect the light signal.
 2. The device of claim 1 wherein the lightsensor is configured to transmit the light signal through fluid directlyoverlying the nozzle.
 3. The device of claim 1, further comprising: alight shield directly overlying the light sensor, the light shieldconfigured to block light signals in a surrounding environment.
 4. Thedevice of claim 1, further comprising: control circuitry configured todetermine whether the nozzle is in a blocked nozzle state based on thedetected light signal.
 5. The device of claim 1 wherein the light sensoris positioned laterally to the nozzle, and is spaced from a sidewall ofthe nozzle by a distance.
 6. The device of claim 5 wherein the distanceis between 10 and 50 micrometers.
 7. The device of claim 1, furthercomprising: a first structural layer on the substrate, the chamber beingformed in the first structural layer; and a second structural layer onthe substrate, the nozzle being formed on the second structural layer.8. The device of claim 7 wherein the light sensor is positioned on thefirst structural layer, and the light emitting device is positioned onthe second structural layer.
 9. The device of claim 1, furthercomprising: readout circuitry configured to read the detected lightsignal from the light sensor.
 10. The device of claim 9 wherein thelight sensor is a photodiode, the readout circuitry includes a firsttransistor and a second transistor, a source of the first transistor iselectrically coupled to a cathode of the photodiode, and a gate of thesecond transistor is electrically coupled to the source of the firsttransistor and the cathode of the photodiode.
 11. The device of claim 9wherein the light sensor is a photodiode, the readout circuitry includesa transistor and an operational amplifier, a source of the transistor iselectrically coupled to a cathode of the photodiode, and the operationalamplifier is electrically coupled to the source of the transistor andthe cathode of the photodiode.
 12. The device of claim 9 wherein thelight sensor is a photodiode, the readout circuitry includes atransistor, an operational amplifier, and a counter, a source of thetransistor is electrically coupled to a cathode of the photodiode, theoperational amplifier is electrically coupled to the source of thetransistor and the cathode of the photodiode, and the counter iselectrically coupled to the operational amplifier.
 13. A device,comprising: a substrate; a first structural layer on the substrate achamber in the first structural layer; a second structural layer on thefirst structural layer a nozzle through the second structural layer andfluidically coupled to the chamber; a fluid ejector between thesubstrate and the first structural layer; a light emitting device on thesecond structural layer, the light emitting device configured totransmit a light signal through fluid positioned at the nozzle; and alight sensor on the first structural layer, the light sensor configuredto detect the light signal transmitted through the fluid positioned atthe nozzle.
 14. The device of claim 13, further comprising: a lightshield on the second structural layer and directly over the lightsensor, the light shield configured to block light signals.
 15. Thedevice of claim 13, further comprising: control circuitry on the firststructural layer, the control circuitry configured to determine whetherthe nozzle is in a blocked nozzle state based on the detected lightsignal.
 16. The device of claim 13 wherein the light sensor ispositioned laterally to the nozzle, and is spaced from a sidewall of thenozzle.
 17. A method, comprising: instructing, during a first timeperiod, a fluidic ejection device to eject fluid out of a nozzle of thefluidic ejection device, the fluidic ejection device including a lightemitting device and a light sensor positioned on opposite sides of thenozzle; emitting, by the light emitting device and during the first timeperiod, a first light signal; measuring, by the light sensor and duringthe first time period, the first light signal; instructing, during asecond time period subsequent to the first time period, the fluidicejection device to stop ejecting fluid out of the nozzle of the fluidicejection device; emitting, by the light emitting device and during thesecond time period, a second light signal; measuring, by the lightemitting device and during the second time period, the second lightsignal; and determining, by control circuitry, whether the fluidicejection device is in a normal state, a blocked nozzle state, or anaccumulated fluid state based on the measured first light signal and themeasured second light signal.
 18. The method of claim 17 wherein thecontrol circuitry determines the fluidic ejection device is in thenormal state in a case where the measured first light signal is above apredetermined threshold and the measured second light signal is belowthe predetermined threshold.
 19. The method of claim 17 wherein thecontrol circuitry determines the fluidic ejection device is in theblocked nozzle state in a case where the measured first light signal isbelow a predetermined threshold and the measured second light signal isbelow the predetermined threshold.
 20. The method of claim 17 whereinthe control circuitry determines the fluidic ejection device is in theaccumulated fluid state in a case where the measured first light signalis above a predetermined threshold and the measured second light signalis above the predetermined threshold.